A via is an electrical connection between wiring structures (e.g., wiring layers) in a physical electronic circuit that goes through the plane of one or more adjacent layers. For example, in integrated circuit design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different wiring layers. A via connecting the lowest layer of metal to diffusion or poly is typically called a “contact”. A through-silicon via (TSV) is a vertical electrical connection (via) passing completely through a silicon wafer or die
TSV plasma processing causes a depletion region of semiconductor (silicon) material adjacent to the TSV. This depletion results in a poor substrate contact and, also, causes a variability in the electrical characteristics of the TSV. This variability affects the ability to carry moderate to high frequency signals. More specifically, TSV processes produce a MOS capacitor in series with the TSV oxide capacitor. The depletion/inversion in the semiconductor (silicon) substrate adds to the impedance of the TSV (which is used for carrying high frequency signals). While the oxide capacitance is fixed by geometry, the series capacitance is a function of doping and processing.